I use LogMeIn a lot to access AC from home and the hospital when patients, the ER calls, etc. So when LogMeIn Ignition for the iPhone came out, I got it. I luckily timed my AT&T contract right, and was able to move right from the original iPhone to the 3GS at the subsidized price. By the way, put the old iPhone on eBay -- the prices are unbelievable -- I got almost $300. My previous Blackberry I couldn't even give away as a paperweight.
In any case, iPhone LogMeIn has been a real lifesaver several times already. The connection with 3G is good, even better with WiFi -- I guess the app must compress the image or something, since the screen download & refresh is fast. I had no trouble in reading the data because you can stretch the image. I wouldn't use it for everyday use, but it's amazing to be able to access AC while rolling down the aisle in the grocery store.